Study On The Synergistic Effect Of MWNTs/TiO₂ Adsorption Photolysis And Pilot Test On Treatment Of Organophosphorus Pesticide Wastewater By Photocatalysis Combined Coagulation

In the process of production and use of organophosphorus pesticides,a lot of waste water is produced,these wastewater is characterized by high organic content,difficult biodegradation,strong toxicity and difficulty in handling,which have caused great harm to the environment and human health.Therefore,it is very important to select the appropriate method to efficiently process organophosphorus pesticide wastewater to meet the target emission.MWNTs/TiO₂ composite catalyst was used to study the synergistic effect of MWNTs/TiO₂ adsorption and photodegradation,and the effect was determined by using MWNTs/TiO₂ and coagulant precipitation in the treatment of omethoate pesticide wastewater.The research contents mainly include the preparation of MWNTs/TiO₂ composite catalysts,the optimization of process conditions,the characterization of MWNTs and MWNTs/TiO₂,the feasibility study of MWNTs/TiO₂ and nano TiO₂ experiment;Study on the synergistic effect of MWNTs/TiO₂ composite catalyst on adsorption and photodegradation of oxyleate;The optimization design of coagulation-photocatalytic oxidation combined treatment device and the pilot test of the combined treatment plant for the treatment of omethoate wastewater.The MWNTs/TiO₂ composite photocatalyst was prepared by sol-gel method,through single factor and orthogonal experiment method,it was concluded that the best preparation conditions is a pH value of 4 sol system,polystyrene sulfonate?PSS?dosing quantity 3 g/L,m?MWNTs?/m?TiO₂?1.25%,calcination temperature 600 ?,calcination time 5.5 hours.The optimized MWNTs,MWNTs/TiO₂ scanning electron microscopy showed that the surface of MWNTs after nitric acid treatment was smoother,less concentrated and more porous,and the length of MWNTs was shortened.In addition,the optimized MWNTs/TiO₂ is more evenly distributed due to the high temperature calcining removal of volatile impurities.MWNTs/TiO₂ EDX characterization results showed that the catalyst mainly contains Ti,O and C elements,whose quality scores are 59.59%,35.72%and 3.58%respectively,it also contains a small amount of Na and S elements.It shows that nano TiO₂ success load on the MWNTs.The removal rate of Omethoate from composite catalyst MWNTs/TiO₂ is significantly higher than that of MWNTs alone adsorption and nano TiO₂ alone photocatalytic degradation removal rate,which fully reflects the synergistic effect of MWNTs/TiO₂ on Omethoate removal.Under different temperature,pH value,MWNTs/TiO₂ dosage,light intensity and stirring speed,MWNTs/TiO₂ has synergistic effect on Omethoate adsorption and photodegradation.The experimental study of coagulation and sedimentation pretreatment of Omethoate solution confirmed that the best operation conditions of coagulation and precipitation to remove Omethoate were:the dosage of Chinese medicine was PAC 150mg/L,Ca?OH?2 67mg/L,PAM 4mg/L,and the initial pH value of Omethoate solution was 11.The photocatalytic degradation of Omethoate solution by MWNTs/TiO₂ showed that the degradation rate of Omethoate was the largest when the pH value of the Omethoate solution was 3,the light intensity is 420W,the dosage of composite catalyst was 900 mg/L,the temperature was 25 degrees,and the stirring speed was 800 r/min.The lower the concentration of Omethoate,the greater the degradation rate,and the catalyst can be reused in the photocatalytic degradation.A pilot scale experiment on the treatment of Omethoate wastewater by coagulation sedimentation-photocatalytic process was carried out.The results showed that when the photocatalytic reaction was carried out at 240 min,the content of Omethoate was below 0.5mg/L and the COD content of solution was below 50 mg/L,which met the first level A emission standard of sewage.MWNTs/TiO₂ removal of organic phosphorus adsorption and photodegradation have synergistic effect,can be more rapid and complete removal of organic phosphorus compounds in wastewater by MWNTs/TiO₂;Using MWNTs/TiO₂ photocatalysis and coagulation precipitation detection,Omethoate wastewater effluent meet the wastewater discharge standard,combination process of organophosphorus pesticide wastewater has more practical value and broad market application prospect.